Received: from localhost (unknown [200.46.204.183]) by mail.postgresql.org (Postfix) with ESMTP id BD55664FE61 for ; Wed, 10 Dec 2008 09:34:24 -0400 (AST) Received: from mail.postgresql.org ([200.46.204.86]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 28708-01 for ; Wed, 10 Dec 2008 09:34:20 -0400 (AST) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from wf-out-1314.google.com (wf-out-1314.google.com [209.85.200.169]) by mail.postgresql.org (Postfix) with ESMTP id 2963E64FC4F for ; Wed, 10 Dec 2008 09:34:19 -0400 (AST) Received: by wf-out-1314.google.com with SMTP id 25so159176wfc.28 for ; Wed, 10 Dec 2008 05:34:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to :subject:cc:in-reply-to:mime-version:content-type :content-transfer-encoding:content-disposition:references; bh=ZiCwwn9/ccejZvXIRbRLOX66+Sh0mvAYX/6srxZiHTw=; b=bPwqf9uOqhAE9djlMH8rntu/+zfRqmRb1LMpNXBDxWJnL1fKT6mFg4xAaTIwBAwu3+ sGsbGOmXLXT4EfPtbSqN/tI+zEaGD7IUMQDJJ5/9TICrNL/HJ79QTQbALAXfVIDg/s0+ lPNVGhlsHlPEIXP63Zc5xFwH6+04kYIX/cWYw= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=PSACo/CZm44HWDQRKwPgXkyubg9ER7A/9Jf7NE2Hirs0MsI66FVg3daajY/353+OBg wt1EMYqIpINeycPmaY2yVUapZFGjIPlsHoDrvWiaosYRPo1vt5nmzYb5FrnMs1E/ipWo VPINMw3Vq28OcwvTdAynMqSpHcTsgEBfLDlQA= Received: by 10.114.197.10 with SMTP id u10mr955840waf.96.1228916058025; Wed, 10 Dec 2008 05:34:18 -0800 (PST) Received: by 10.114.167.5 with HTTP; Wed, 10 Dec 2008 05:34:17 -0800 (PST) Message-ID: Date: Wed, 10 Dec 2008 06:34:17 -0700 From: "Scott Marlowe" To: "Mario Weilguni" Subject: Re: Experience with HP Smart Array P400 and SATA drives? Cc: "Aidan Van Dyk" , "Joshua D. Drake" , pgsql-performance@postgresql.org In-Reply-To: <493FB619.5060205@sime.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <4934FE60.30702@sime.com> <493E6023.3030800@sime.com> <1228838308.13962.0.camel@jd-laptop.pragmaticzealot.org> <20081209161750.GO26596@yugib.highrise.ca> <493FB619.5060205@sime.com> X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=0 tagged_above=0 required=5 tests=none X-Spam-Level: X-Archive-Number: 200812/113 X-Sequence-Number: 32149 On Wed, Dec 10, 2008 at 5:29 AM, Mario Weilguni wrote: > Aidan Van Dyk schrieb: >> >> * Joshua D. Drake [081209 11:01]: >> >>> >>> Yes the SmartArray series is quite common and actually know to perform >>> reasonably well, in RAID 10. You still appear to be trying RAID 5. >>> >> >> *boggle* >> Are people *still* using raid5? >> >> /me gives up! >> >> > > Why not? I know it's not performing as good as RAID-10, but it does not > waste 50% diskspace. RAID-6 is no option, because the performance is even > worse. And, on another system with RAID-5 + spare and SAS drives, the same > controller is working very well. I wouldn't refer to it as "waste". It's a tradeoff. With RAID-10 you get good performance at a cost of having 1/2 the storage capacity of your drives combined. RAID-5 says you're more worried about your budget than performance, and sometimes that's the case. The production servers where I work run a 25G database on a 12 disk RAID-10. The fact that we get less than a terabyte from 12 147G scsi disks is no great loss to us, we're interested in having a disk array that can handle a few 100 transactions per second even if a disk dies. Also, RAID-6 is faster, IF one of your disks has died (and you're on a good RAID controller). RAID-5 degraded performance is abysmal even on good controllers. RAID-10 with a lost disk is about the same as RAID-10 with all its disks in terms of performance. If you're running a production 24/7 database server, you can't afford to lose 80%+ of your throughput when a single drive fails. But this has all been covered before (many times) both on this list and over the internet. RAID-5 is useful for large data stores that can afford downtime. And there are plenty of apps like that. If your app isn't like that, i.e. needs to be up and performing well 24/7, or close to it, then RAID5 is a tragic mistake to make.